The invention relates to semiconductor devices, and more particularly to fuse structures and integrated circuit devices comprising the same.
Fuses are frequently used to reconfigure memory and logic circuitry. For example, in dynamic or static memory chips, defective memory cells or circuitry may be replaced by blowing fuses associated with the defective circuitry while activating redundant circuitry to form new memory circuits. This circuit rerouting using blowable fuse links contributes to enhanced yields without the necessity of scrapping defective process wafers.
Generally, fuse links, made of a conductive material, such as a metal may be blown or removed by passing an excessive current through the circuitry which melts the fuse link, or exposing the fuse link to intense laser irradiation to ablate the fuse link including a window of a thin transparent layer of oxide insulating material above the fuse link.
One problem with a metal fuse link is the relatively large size thereof, which is difficult to reduce. The metal fuse link is blown by an external energy source, such as a laser beam, to thereby limit their formations near a top portion of an integrated circuit chip.
Thus, another type of fuse link referred to as poly fuse (“polysilicon” or “poly resistor” fuse) has recently been introduced. One advantage of the poly fuse link over the metal fuse link is the lower amount of current required to open the fuse element during programming and is allowed to be disposed in an internal part of an integrated circuit chip. Typical poly fuses in a fuse array exhibit a pre-burned resistance of 30-100 ohms and incorporate metal silicide such as nickel (Ni) silicide. In order to burn (or blow) the poly fuses in a fuse cell effectively, a relatively high fuse programming voltage is required. Currently, however, the highest fuse programming voltage applied to poly fuses in a fuse array is typically limited to the common chip core burn-in voltage (Vcc) to ensure reliability. Unfortunately, the common chip core burn-in voltage (Vcc) is sometimes not sufficient to effectively program the fuses in the fuse array. In addition, the metal silicide used in the poly fuse may cause current leakage after blow up thereof. As a result, the fuse programming failure rate in a fuse array is high and, likewise, current leakage may occur near a place where the poly fuse blew up.